The present studies are designed to study the mechanisms responsible for the occurrence of arthralgia and arthritis after immunization with live attenuated rubella virus vaccine in man. It is also proposed to learn whether natural or vaccine induced rubella virus infection is in anyway related to the course and pathogenesis of chronic rheumatoid joint disease in childhood. The techniques of routine serologic testing, tissue culture infectivity, radioimmunodiffusion, immunofluorescene, in-vitro lymphocyte transformation and mixed lymphocyte cultures will be employed to investigate the specific problem outlined above.